Following the big freeze, and having a narrow escape with a frozen waste pipe going to an outside drain, I want to re-plumb the pipe to go down the toilet stack in the cloakroom it passes, on it's way out the wall.
I know you can get 90degree pan connectors with a fitting to accept a waste pipe - so that side is sorted. However I am worried about siphonage, when the toilet is flushed.
A lot of googling (why are plumbing matters so off-grid ?) and a phone call to a local plumbers merchants suggests an anti-siphon trap
Does this seem practical, sensible, and the correct way ? Presumably I will need two (although the shop guy said one on the basin - the washing machine wouldn't need one as it was so long ???????)
cheers guys.